This invention relates to blocks used for retaining walls, parapet walls, or for free-standing walls. In particular, this invention relates to an apparatus and method for creating a desired appearance and shape to a wall block.
Retaining walls are used in various landscaping projects and are available in a wide variety of styles. Numerous methods and materials exist for the construction of retaining walls. Such methods include the use of natural stone, poured concrete, precast panels, masonry, and landscape timbers or railroad ties.
In recent years, segmental concrete retaining wall units, which are dry stacked (i.e., built without the use of mortar), have become widely accepted in the construction of retaining walls. One such unit is described in U.S. Pat. No. Re 34,314 (Forsberg) and another is described in U.S. Pat. No. 6,149,352 (MacDonald). Such retaining wall units have gained popularity because they are mass produced and, consequently, relatively inexpensive. They are structurally sound, easy and relatively inexpensive to install, and couple the durability of concrete with the attractiveness of various architectural finishes. Successful wall systems include, among other design elements, a pinning system that interlocks and aligns the retaining wall units, thereby providing structural strength and allowing efficient installation. Such systems are advantageous in the construction of larger walls, when combined with the use of geogrids hooked over the pins, as described in U.S. Pat. No. 4,914,876 (Forsberg).
Another important feature of retaining wall blocks is the appearance of the block. The look of weathered natural stone is very appealing for retaining walls. There are several methods in the art to produce concrete retaining wall blocks that mimic the look of natural stone. One well known method is to split the block during the manufacturing process so that the front face of the block has a fractured concrete surface that looks like a natural split rock. This method produces blocks with a vertical split face, but cannot produce a rounded or fractured top and bottom edge which may be a key feature of natural or quarried stone. Another method is to form blocks individually in a mold and texture the surfaces by removal of the mold. Additional machine texturing processes can then be applied.
Because of the natural variation in size of the stones used in stone retaining walls, the wall surface has variations in width from stone to stone. A wall block system capable of duplicating the appearance of natural stone walls is described in U.S. Pat. No. 6,149,352 (MacDonald), hereby incorporated herein by reference in its entirety. This system uses blocks of different widths and a connection system comprising a channel on each block and multiple pin receiving cavities to align the blocks. Thus this system can be used to produce a wall having random variations in face width and high structural integrity of the wall structure.
Another method to create a weathered stone appearance is to tumble the blocks together with other blocks in a large rotating canister. The collisions of the blocks in the tumbler chips off random pieces of the blocks, rounding the edges and creating a look that can be quite close to the appearance of a natural stone. This is a labor-intensive undertaking that also can result in undesirable damage to the blocks, blocks covered with dust, the environmental aspect of dealing with the dust by-product of tumbling and the high overall costs of production.
Another method to make naturally appearing blocks has been described in U.S. Pat. Nos. 5,078,940 and 5,217,630 (both to Sayles). These patents describe a method and an apparatus for manufacturing a concrete block having an irregular surface. The irregular surface can be made to look similar to split stone, and thus is very desirable. The process involves filling a mold cavity that has a plurality of projections with uncured block material (e.g., concrete) and causing a portion of the material, in the area designated to be the finished face(s), to be retained in place relative to the cavity walls when the block is removed from the cavity. This results in a split appearance for the surface, without having to perform the splitting operation. This is an advantage because the expense and time of conventional block splitting is avoided.
Other methods of molding to produce textured surfaces for a block include, for example, U.S. Pat. No. 6,224,815 (LaCroix et al.), in which a block mold is used to produce two blocks having a roughened or textured face. The mold has two cavities separated by a grate. The surfaces that face the grate have a roughened texture upon removal of material from the mold. The advantage to this arrangement is stated to be that the mold is self-cleaning. Another mold for producing a textured block surface is described in U.S. Pat. No. 6,138,983 (Sievert). This mold has upper and lower lips along at least one side wall. A lip or lips serve to strip material from the block as it is being removed from the mold, thus producing a roughened, or split, appearance to the block. Typically, retaining wall blocks are manufactured to have the desired appearance on the front face (i.e., the outer face of a wall) only. In the patents described above, the pattern or design is typically provided only to the front face because that is the only portion of the retaining wall block that is visible after the wall is constructed. Sometimes a portion of a side surface may be provided with a desired pattern or texture. In the Sayles"" patents described above, a natural or split look is obtained for only the front face. Such blocks do not allow the user the option to use either the front, side, or back faces of the block interchangeability as the exposed xe2x80x9cfront facexe2x80x9d.
To create a wall block that has a roughened texture on the front, side and back surfaces poses certain problems. If a splitting method is used, multiple splits and two orientations for the splits are required to create a quadrilateral block with texture on three sides. In addition, when two opposing block units are split apart, there is typically little waste. However, when more than two sides are split, a waste slab is required. This adds to the expense and labor of processing the block.
Tumbling methods are also used to texture a block""s surfaces. However, tumbling cannot be used when a block has a lip (often used for connecting and stabilizing blocks in a wall) or if the block has large voids (e.g., cores) or other elements that would be knocked off or destroyed by tumbling. In addition, if a tumbling method is used, substantial portions of the block faces will be ground smooth and not necessarily natural looking. Tumbling also is an expensive production method because blocks must be formed, cured sufficiently to withstand a tumbling process (e.g., typically for a minimum of 7 days and then transported to a tumbler for treatment. If the method combines both splitting and tumbling, the production costs, and thus the cost to the consumer, can be undesirably high.
It would be desirable to provide a way to produce a block with an overall weathered appearance as well as rounded edges which avoids the need for tumbling, and thus potentially damaging, a block. In addition, a method is needed to produce the desired appearance on at least three sides of a block that would avoid the need for tumbling the block.
This invention is an apparatus and a method for treating the surfaces and edges of a block to mimic the appearance of natural stone. This invention produces blocks having a natural, weathered appearance but avoids the damage, breakage, and expense associated with existing methods, such as splitting or tumbling. This invention also avoids producing heavily dust-coated blocks caused by the tumbling process. This is very desirable because the dust coating on the blocks is difficult to remove in a factory environment and can adhere to the blocks if they are exposed to water while stored in inventory. The present invention allows the treatment of up to four sides of a block, can be adjusted to provide varying degrees of surface and edge treatment, and is capable of keeping pace with high volume block production equipment with a negligible amount of dust.
The apparatus and method of this invention is useful for blocks used for purposes other than retaining walls, including any block in which a natural stone appearance is desirable. Though it is contemplated that the material comprising the blocks is concrete, it is further to be understood that the apparatus and method could be used with any suitable material, including slabs of natural stone.
The apparatus and method of this invention are desirable in a production environment due to rapid throughput and minimal product loss.
In one aspect, this invention is a method for treating the surface of a block, the block having an upper surface opposed to a lower surface, first and second opposed faces joining the upper and lower surfaces of the block to form upper and lower face edges, and first and second side surfaces joining the upper and lower surfaces of the block to form upper and lower surface edges, the method comprising positioning the block in a first treatment station including an edge rounding member; treating the block in the first treatment station to round the upper and lower face edges of at least one of the first and second opposed faces of the block; positioning the block in a second treatment station including a surface roughening member; and treating the block in the second treatment station to roughen a surface of at least one of the first and second opposed faces. The edge rounding member may comprise hammer elements. The surface roughening member may comprise flailing elements. The block may be immobilized in the first treatment station and the block may move through the second treatment station as the surface is roughened. The method may further comprise rotating the block within the first treatment station and treating the block to round the upper and lower surface edges of the at least one of the first and second side surfaces of the block and rotating the block within the second treatment station, and treating the block to roughen surface of the at least one of the first and second side surfaces. The block may move to a third treatment station including an edge rounding member, and be treated there to round the upper and lower surface edges of at least one of the first and second side surfaces of the block. The block may move to a fourth treatment station that includes a surface roughening member; and be treated to roughen the surface of at least one of the first and second side surfaces.
The hammer elements may comprise a segment having a plurality of teeth and the flailing elements may comprise hardened steel elements.
In another aspect, this invention is a method for treating the surface of a block by positioning the block in a first hammer station; treating the block in the first hammer station to round at least one of the upper and lower face edges of at least one of the first and second opposed faces the block; positioning the block in a first flail station; and treating the block in the first flail station to roughen a surface of at least one of the first and second opposed faces. The block may be immobilized in the first hammer station and it may move through the second treatment station as the surface is roughened. This method may further comprise rotating the block within the first hammer station and treating the block to round the upper and lower surface edges of the at least one of the first and second side surfaces of the block; as well as rotating the block within the first flail station and treating the block to roughen the surface of the at least one of the first and second side surfaces. The block may be moved to a second hammer station and treated to round the upper and lower surface edges. The block may move to a second flail station including a surface roughening member; and be treated in the second flail station to roughen one of the first and second side surfaces.
In a further aspect, this invention is an apparatus for treating the surface of a block, comprising a first treatment station having an edge rounding member configured to round the upper and lower face edges of at least one of the first and second opposed faces of the block; a second treatment station having a surface roughening member configured to roughen a surface of the at least one of the first and second opposed faces; and a first conveying member for moving the block from the first treatment station to the second treatment station. The apparatus may include a rotating member configured to rotate the block and a clamp to hold the block in the first treatment station. It may include a conveying means to move the block through the second treatment station while the surface is being roughened. The apparatus may further comprise a third treatment station having an edge rounding member configured to round of the upper and lower surface edge, and a fourth treatment station having a surface roughening member configured to roughen the surface of at least one of the first and second side surfaces. It may include a second conveying member for moving the block from the second treatment station to the third treatment station and a third conveying member for moving the block from the third treatment station to the fourth treatment station. The hammer elements may comprise a segment having a plurality of teeth and the segment may be linear or arcuate.
In another aspect, this invention is an apparatus for shaping the surface of a block comprising means for rounding the upper and lower face edges of at least one of the first and second opposed faces of the block; means for roughening a surface of at least one of the first and second opposed faces of the block; and means for moving the block between the rounding means and the roughening means. There may be means for rounding the upper and lower surface edges of the side surfaces, and means for roughening the side surfaces. The apparatus may include means for immobilizing the block and means for conveying the block.
In a further aspect, this invention is an apparatus for treating the surface of a block, comprising a first treatment station having a hammer element configured to round the upper and lower face edges of at least one of the first and second opposed faces of the block; a second treatment station having a flailing element configured to roughen a surface of at least one of the first and second opposed faces; and a pusher for moving the block from the first treatment station to the second treatment station. The apparatus may include a turntable, a clamp to hold the block, and means to convey the block from one station to another.
In a further aspect, this invention is a method of making wall blocks comprising forming the blocks in a mold which imparts a roughened surface texture to at least one of the faces of the blocks; removing the blocks from the mold; positioning at least one of the blocks in a first treatment station; and rounding the upper and lower face edges of the at least one face of the at least one block having a roughened surface texture in the first treatment station without tumbling the at least one block together with other blocks in a block tumbler. The method may include curing the blocks, and may further include positioning the at least one block in a second treatment station; and treating the at least one block to further roughen at least one face having a roughened surface texture.
In another aspect, this invention is a method of making wall blocks comprising forming the blocks in a mold which imparts a roughened surface texture to at least one of the faces of the blocks; removing the blocks from the mold; positioning at least one of the blocks in a first treatment station including an edge rounding member; rounding the upper and lower face edges of the at least one face of the at least one block having a roughened surface texture in the first treatment station without tumbling the at least one block together with other blocks in a block tumbler; positioning the at least one block in a second treatment station including a surface roughening member; and further roughening the surface of the at least one face having a roughened surface texture in the second treatment station.
In a further aspect, this invention is a method of making wall blocks comprising forming the blocks in a mold; removing the blocks from the mold; positioning at least one of the blocks in a first treatment station; and rounding the upper and lower face edges of at least one of the first and second opposed faces of the at least one block in the first treatment station without tumbling the at least one block together with other blocks in a block tumbler. This method may include curing the blocks and positioning a block in a second treatment station and treating it to roughen a surface of a block face. Hammer elements may round the upper and lower face edges and flailing elements may roughen the surface.
In another aspect, this invention is a method of making wall blocks comprising forming the blocks in a mold; removing the blocks from the mold; positioning the blocks in a first treatment station including an edge rounding member; rounding the upper and lower face edges of at least one of the first and second opposed faces of the blocks in the first treatment station; positioning the blocks in a second treatment station including a surface roughening member; and roughening at least one of the first and second opposed faces in the second treatment station.
In a further aspect, this invention is a method for treating the surface of a block comprising positioning the block in a first treatment station including an edge rounding member; treating the block in the first treatment station to round at least one of the upper and lower face edges of at least one of the first and second opposed faces of the block; positioning the block in a second treatment station including a surface roughening member; and treating the block in the second treatment station to roughen a surface of at least one of the first and second opposed faces.
In another aspect, this invention is a method of making wall blocks comprising forming the blocks in a mold which imparts a roughened surface texture to at least one of the faces of the blocks; removing the blocks from the mold; positioning at least one of the blocks in a first treatment station; and rounding at least one of the upper and lower face edges of the at least one face of the at least one block having a roughened surface texture in the first treatment station without tumbling the at least one block together with other blocks in a block tumbler.